Effect of Asymmetrical Versus Symmetrical Extremity Exercises on Erector Spinae Co-Contraction: A Pilot Study in Healthy Adults

Background. Idiopathic scoliosis (IS) is commonly associated with asymmetrical erector spinae (ES) muscle activity, contributing to impaired spinal stability and postural imbalance. Physiotherapy exercise programmes are widely used in the conservative management of IS; however, limited evidence exists regarding the comparative effects of symmetrical and asymmetrical upper limb (UL) and lower limb (LL) exercises on ES muscle co-contraction at specific vertebral levels. Therefore, this pilot experimental study aimed to compare the effects of symmetrical and asymmetrical extremity exercises on ES muscle co-contraction at vertebral levels T7, T12, and L3 in healthy adults using surface electromyography (sEMG). Methods. A quantitative pilot experimental study was conducted with 21 healthy participants (16 males, 5 females). Bilateral ES muscle activity was recorded using sEMG at vertebral levels T7, T12, and L3 during four exercises: barbell shoulder press, dumbbell shoulder press, weighted squat, and dumbbell single-leg squat. Electromyographic signals were normalized using maximum voluntary isometric contraction (MVIC). Results. Symmetrical UL exercises produced significantly greater right ES muscle co-contraction than asymmetrical UL exercises at T7, T12, and L3 (all p = 0.001). Median right ES activation at T7 was higher during the barbell shoulder press compared to the dumbbell shoulder press (64.09 vs. 34.81). Similarly, symmetrical LL exercises demonstrated greater right ES activation at T7 and T12 compared to asymmetrical LL exercises (both p = 0.001), with median T7 activation values of 73.51 versus 50.67, respectively. Asymmetrical exercises demonstrated relatively greater contralateral ES activation, particularly at T7 and T12, although left-side differences between exercise categories were not statistically significant across most comparisons. Conclusion. Symmetrical extremity exercises elicited greater erector spinae co-contraction, whereas asymmetrical exercises preferentially activated the contralateral erector spinae, providing preliminary evidence to inform exercise selection for trunk muscle rehabilitation pending validation in individuals with idiopathic scoliosis.